Resin-encapsulated semiconductor apparatus and process for its fabrication

ABSTRACT

The present invention provides a resin-encapsulated semiconductor apparatus comprising a semiconductor device having a ferroelectric film and a surface-protective film, and an encapsulant member comprising a resin; the surface-protective film being formed of a polyimide. The present invention also provides a process for fabricating a resin-encapsulated semiconductor apparatus, comprising the steps of forming a film of a polyimide precursor composition on the surface of a semiconductor device having a ferroelectric film; heat-curing the polyimide precursor composition film to form a surface-protective film formed of a polyimide; and encapsulating, with an encapsulant resin, the semiconductor device on which the surface-protective film has been formed. The polyimide may preferably have a glass transition temperature of from 240° C. to 400° C. and a Young&#39;s modulus of from 2,600 MPa to 6 GPa. The curing may preferably be carried out at a temperature of from 230° C. to 300° C.

[0001] This application is based on application No. H9-9276 filed inJapan, the content of which is incorporated hereinto by reference.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] This invention relates to a resin-encapsulated semiconductorapparatus having a semiconductor device with a ferroelectric film, and aprocess for its fabrication.

[0004] 2. Description of the Related Art

[0005] In recent years, non-volatile or large-capacity semiconductormemory devices having thin films of ferroelectric substances (dielectricmaterials having a high dielectric constant, or substances having aperovskite crystalline structure) have been proposed. Ferroelectricfilms have features such as self polarization and high dielectricconstant characteristics. Hence, the ferroelectric films have hysteresischaracteristics between polarization and electric fields offerroelectric substances, and their utilization enables materializationof non-volatile memories. Also, the ferroelectric films have such alarger dielectric constant than silicon oxide films that memory cellscan be made to have a smaller area when the ferroelectric films are usedas capacitive insulation films, to enable materialization oflarge-capacitance highly integrated RAMs (random access memories).

[0006] The ferroelectric films are comprised of a sintered body of ametal oxide, and contain much oxygen which is rich in reactivity. Whencapacitors are formed by using such ferroelectric films in thecapacitive insulation films, it is indispensable, in the upper and lowerelectrodes of the capacitive insulation films, to use a substance whichis stable to oxidation reaction, as exemplified by an alloy chieflycomposed of platinum.

[0007] After capacitors, interlayer insulation films and so forth havebeen formed, passivation films are formed on the outermost surfaces ofthe devices. Silicon nitride or silicon oxide is used in the interlayerinsulation films and passivation films, which are usually formed by CVD(chemical vapor deposition) and hence hydrogen is often incorporated inthe films.

[0008] When semiconductor apparatuses making use of such ferroelectricfilms are used in electronic equipment for public use, they are requiredto be inexpensive resin-encapsulated semiconductor apparatuses havinggood mass productivity. In particular, ferroelectric non-volatilememories are greatly needed for portable equipment as memoriessubstituting flash memories, because of their properties such as lowpower, low voltage, and non-volatility making refresh operationunnecessary, and the resin-encapsulated semiconductor apparatuses arealso desired in order to provide thin type packages.

[0009] At present, however, devices that utilize the ferroelectric filmsas capacitive insulation films are chiefly held by ceramic-encapsulatedproducts, and almost no resin-encapsulated products are available.Devices with a large capacity are also not yet developed. This isbecause the polarization characteristics of ferroelectric filmsdeteriorate as a result of heat treatment.

[0010] Capacitors having ferroelectric films are known to undergodeterioration of polarization characteristics upon their annealing in anatmosphere of hydrogen (Lecture Collections in '96 Ferroelectric FilmMemory Technique Forum, published by K.K. Science Forum, No. 4, page 4,lines 1-12). This deterioration is presumed to be caused by the platinumof upper and lower electrodes which reacts with hydrogen to act as areducing catalyst to reduce the ferroelectric film. In particular, inthe case of large-capacity highly integrated devices, the ferroelectricfilms are fine in size, and hence this deterioration of thecharacteristics of the capacitors is forecasted to greatly affect thecharacteristics of the overall devices.

[0011] In the resin-encapsulating of semiconductor devices by transfermolding, encapsulant resins containing fillers (usually silica) areused. The fillers contained in encapsulant resins, however, have suchhard particles that the fillers may damage the device surfaces whenencapsulated. Moreover, since ferroelectric materials exhibitpiezoelectricity, the characteristics of ferroelectric films may changeupon application of a pressure to the ferroelectric film inside thedevices when encapsulated. In the fabrication of DRAMs (dynamic randomaccess memories), α-rays are emitted from radioactive componentscontained in the fillers, to cause memory soft errors in some cases.Accordingly, in order to prevent the device surfaces from being damagedby the fillers, to prevent application of pressure to the ferroelectricfilms and to screen α-rays being emitted from the fillers, protectivefilms comprised of polyimide must be previously formed on the devicesurfaces. Such surface-protective polyimide films are formed byheat-curing polyimide precursor composition films usually at atemperature of about 350 to 450° C. When such a polyimide precursor isheat-cured, the hydrogen contained in the passivation films orinterlayer insulation films may diffuse to cause a deterioration ofpolarization characteristics of the ferroelectric films. Thus, noresin-encapsulated products of devices in which thermoplastic resins areused as surface-protective films are known at present.

SUMMARY OF THE INVENTION

[0012] An object of the present invention is to provide aresin-encapsulated semiconductor apparatus having a ferroelectric filmwith good polarization characteristics and having a high reliability,and a process for its fabrication.

[0013] Studies made on conditions under which ferroelectric films causethe deterioration of polarization characteristics have revealed that thedeterioration occurs when heated at above 300° C. The present inventorsthought that the surface-protective polyimide films could be heat-curedat below 300° C. However, when conventional polyimide precursors areused, which cure at such a low temperature, the resultantresin-encapsulated semiconductor apparatuses had a problem in theirsolder reflow resistance.

[0014] At present, as methods for packaging resin-encapsulatedsemiconductor apparatuses on printed-wiring substrates, face-downmounting is prevalent. The face-down mounting employs a solder reflowingmethod, in which leads of a semiconductor device and wiring of aprinted-wiring substrate are provisionally joined with a cream solderfollowed by heating of the entire semiconductor device and substrate tosolder them. As methods sorted according to how heat is applied,infrared reflowing and vapor phase reflowing are known, the former beinga method utilizing infrared radiated heat and the latter being a methodutilizing condensation heat of fluorinated inert liquid.

[0015] As encapsulant resin, epoxy resin is usually used. This epoxyresin always absorbs moisture in an ordinary environment. At the time ofsolder reflow soldering, resin-encapsulated semiconductor apparatusesare exposed to high temperatures of from 215 to 260° C. Hence, when theresin-encapsulated semiconductor apparatuses are packaged on thesubstrate by reflow soldering, the abrupt evaporation of water causescracks in the encapsulant resin to bring about a serious problem in viewof the reliability of semiconductor devices. Accordingly, in the past,various improvements have been made from the viewpoint of making theencapsulant resin have a lower moisture absorption and have a highadhesion performance (Thermosetting Resins, Vol. 13, No. 4, published1992, page 37, right column, lines 8-23).

[0016] The present inventors have examined resin cracks produced inconventional resin-encapsulated semiconductor devices, and have foundthat peeling occurs at the interface between the devicesurface-protective polyimide film and the encapsulant resin, and thatthis is the starting point of causing cracks in the encapsulant resin.They have also found that this peeling is influenced by physicalproperties of surface-protective films, in particular, glass transitiontemperature and Young's modulus.

[0017] Now, as a result of further detailed studies, it has been foundthat ferroelectric films may cause less deterioration of polarizationcharacteristics when the device surface-protective polyimide films areformed by heat treatment in the temperature range of from 230° C. to300° C. It has been also found that, when the polyimide formed at suchheat treatment temperature has a glass transition temperature of from240° C. to 400° C. and a Young's modulus of from 2,600 MPa to 6 GPa, theresin-encapsulated semiconductor apparatus has a superior solder reflowresistance and no peeling may occur at the interface between the devicesurface-protective polyimide film and the encapsulant resin, promisinghigh reliability.

[0018] Based on these new findings, the present invention provides aresin-encapsulated semiconductor apparatus comprising a semiconductordevice having a ferroelectric film and a surface-protective film, and aencapsulant member comprising a resin, the surface-protective film beingformed of a polyimide. The present invention has first made it possibleto materialize such a device for the first time.

[0019] The present invention also provides a process for fabricating aresin-encapsulated semiconductor apparatus, the process comprising thesteps of;

[0020] forming a polyimide precursor composition film on the surface ofa semiconductor device having a ferroelectric film;

[0021] heat-curing the polyimide precursor composition film to form asurface-protective film formed of a polyimide; and

[0022] encapsulating with a encapsulant resin the semiconductor deviceon which the surface-protective film has been formed.

[0023] The polyimide used in the present invention as a material for thesurface-protective film may preferably have a glass transitiontemperature of from 240° C. to 400° C. and a Young's modulus of from2,600 MPa to 6 GPa. Use of such a polyimide makes it possible to obtaina semiconductor device having a high reliability, without causing anycracks even by reflow soldering. The polyimide precursor compositionfilm may preferably be heat-cured at a temperature of from 230° C. to300° C., but may be done at a temperature higher than 300° C. so long asthe heat treatment is carried out at 350° C. or below for a short time(usually within 4 minutes, depending on the heat resistance ofsemiconductor devices) and also the polyimide film thus formed has aYoung's modulus of 3,500 MPa or above and a glass transition temperatureof 260° C. or above, thus the objects of the present invention can beachieved without causing any deterioration of polarizationcharacteristics of the ferroelectric film.

[0024] Incidentally, the fabrication process of the present inventionmay also be applied to resin-encapsulated laminates in which polyimidefilms are used for purposes other than surface-protective films, e.g.,insulating films.

BRIEF DESCRIPTION OF THE DRAWINGS

[0025]FIG. 1 is a cross-sectional view of an LOC (lead on chip) typeresin-encapsulated semiconductor apparatus.

[0026]FIGS. 2A to 2F illustrate an example of a process for fabricatingthe resin-encapsulated semiconductor apparatus.

[0027]FIG. 3 is a cross-sectional view of a resin-encapsulatedsemiconductor apparatus fabricated in Example 1.

[0028]FIG. 4 is a cross-sectional view of a semiconductor device havinga ferroelectric film.

DETAILED DESCRIPTION OF THE INVENTION

[0029] As a polyimide precursor preferable in the present invention,which can obtain the polyimide having a glass transition temperature offrom 240° C. to 400° C. and a Young's modulus of from 2,600 MPa to 6 GPaby heat-curing it at 230° C. to 300° C., it may include polyamic acidscomprised of a repeating unit represented by the following generalformula (I).

[0030] wherein R¹ is at least one of tetravalent aromatic organic groupsshown in the following chemical formula group (II), and R² is at leastone of divalent aromatic organic groups shown in the following chemicalformula groups (III) and (IV).

[0031] Of these polyamic acids, polyamic acids wherein R¹ is at leastone of those listed in the following chemical formula group (VII) and R²is at least one of those listed in the following chemical formula group(VIII) are particularly suited to the present invention.

[0032] In particular, those shown in the following chemical formulas(XIV) and (XVI) to (XVIII) are suited to the present invention. Ofthese, a polyamic acid comprised of a repeating unit represented by thechemical formula (XVI) is most preferred.

[0033] The polyamic acid used in the present invention may further have,in addition to the unit represented by the formula (I), a repeating unithaving the same structure as the one represented by the above generalformula (I) but having a siloxane group as R², so long as it is not morethan 10.0 mol % of the number of total repeating units. Here, thesiloxane group used as R² may be an aromatic siloxane group, and may beat least one of groups having the structure represented by the followingchemical formula group (VI).

[0034] The polyimide precursor composition can be formed into films by,e.g., when the composition is in the form of a liquid or a varnish,coating or spraying the composition on the device surface, optionallyfollowed by heating to bring it into a half-cured state (a state of notcompletely being made into imide). For example, a means such as rotarycoating using a spinner may be used. The coating film thickness may beadjusted according to coating means, solid concentration of thepolyimide precursor composition, viscosity and so forth. When thepolyimide precursor composition is in the form of a sheet, it may beplaced on or stuck to the device surface to form a film.

[0035] The surface-protective film often has openings formed in order tolay the underlying layer bare at the desired portions, e.g., at bondingpads. To form such openings, a resist film may be formed on the surfaceof the polyimide precursor composition film standing half-cured or thepolyimide film having been cured, followed by pattern processing by aconventional fine processing technique, and then the resist film may beremoved. When the openings are formed in a half-cured state, the patternprocessing is followed by heat treatment to completely cure the coating.

[0036] When the polyimide precursor composition is a photosensitivecomposition, the composition film may be exposed to light through a maskwith a given pattern and then the unexposed areas may be dissolved andremoved using a developing solution, followed by heat curing to form apolyimide film with the desired pattern.

[0037] Accordingly, the polyimide precursor composition used in thepresent invention may preferably be a photosensitive polyimide precursorcomposition containing the above polyamic acid and further containing anamine compound having carbon-carbon double bonds, a bisazide compound, aphotopolymerization initiator and/or a sensitizer.

[0038] The amine compound may specifically include, as preferredexamples, 2-(N,N-dimethylamino)ethyl acrylate,2-(N,N-dimethylamino)ethyl methacrylate, 3-(N,N-dimethylamino)propylacrylate, 3-(N,N-dimethylamino)propyl methacrylate,4-(N,N-dimethylamino)butyl acrylate, 4-(N,N-dimethylamino)butylmethacrylate, 5-(N,N-dimethylamino)pentyl acrylate,5-(N,N-dimethylamino)pentyl methacrylate, 6-(N,N-dimethylamino)hexylacrylate, 6-(N,N-dimethylamino)hexyl methacrylate,2-(N,N-dimethylamino)ethyl cinnamate, 3-(N,N-dimethylamino)propylcinnamate, 2-(N,N-dimethylamino)ethyl-2,4-hexadienoate,3-(N,N-dimethylamino)propyl-2,4-hexadienoate,4-(N,N-dimethylamino)butyl-2, 4-hexadienoate,2-(N,N-diethylamino)ethyl-2, 4-hexadienoate and3-(N,N-diethylamino)propyl-2,4-hexadienoate.

[0039] Any of these may be used alone or in the form of a mixture of twoor more, and may be mixed in a proportion of from 10 parts by weight to400 parts by weight based on 100 parts by weight of the polyamide acidpolymer.

[0040] The bisazide compound may specifically include, as preferredexamples, compounds listed in the following chemical formula groups (IX)and (X). Any of these compounds may be used alone or in the form of amixture of two or more, and may be mixed in a proportion of from 0.5part by weight to 50 parts by weight based on 100 parts by weight of thepolymer.

[0041] As examples of the photopolymerization initiator and sensitizer,they specifically include, but are not limited to, Michler's ketone,bis-4,4′-diethylaminobenzophenone, benzophenone, benzoyl ether, benzoinisopropyl ether, anthrone, 1,9-benzoanthrone, acridine, nitropyrene,1,8-dinitropyrene, 5-nitroacetonaphthene, 2-nitrofluorene,pyrene-1,6-quinone-9-fluorene, 1,2-benzoanthraquinone, anthanthrone,2-chloro-1,2-benzoanthraquinone, 2-bromobenzoanthraquinone,2-chloro-1,8-phthaloylnaphthalene, 3,5-diethylthioxanthone,3,5-dimethylthioxanthone, 3,5-diisopropylthioxanthone, benzyl,1-phenyl-5-mercapto-1H-tetrazole, 1-phenyl-5-Mertex,3-acetylphenanthrene, 1-indanone, 7-H-benz[de]anthracen-7-one,1-naphthol aldehyde, thioxanthen-9-one, 10-thioxanthenone and3-acetylindol. Any of these may be used alone or in the form of amixture of two or more of them. The photopolymerization initiator andsensitizer used in the present invention may preferably be mixed in aproportion of from 0.1 part by weight to 30 parts by weight based on 100parts by weight of the polymer.

[0042] As an exposure light source used in the above patterning, whichis carried out by photolithography, any of ultraviolet rays, as well asvisible light rays and radiation rays, may be used.

[0043] The developing solution may include non-protonic polar solventssuch as N-methyl-2-pyrrolidone, N-acetyl-2-pyrrolidone,N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide,hexamethylphosphramide, dimethylimidazolidinone, n-benzyl-2-pyrrolidone,N-acetyl-ε-caprolactam and γ-butylolactone, any of which are used alone,and solutions of a mixture of any of poor solvents for polyamic acid,such as methanol, ethanol, isopropyl alcohol, benzene, toluene, xylene,methyl cellosolve and water, and any of the above non-protonic polarsolvents, either of which may be used.

[0044] The pattern formed by development is subsequently washed with arinsing solution to remove the developing solution. As the rinsingsolution, a poor solvent for polyamic acid, having a good miscibilityfor the developing solution may preferably be used, and may include, aspreferred examples, the above methanol, ethanol, isopropyl alcohol,benzene, toluene, xylene, methyl cellosolve and water.

[0045] The heat treatment to heat-cure the polyimide precursorcomposition film may respectively be carried out by heating using a hotplate. Use of the hot plate enables imidation and film formation ofpolyimide precursor materials in a shorter time than heat treatmentemploying a furnace such as an oven furnace or a diffusion furnace.Thus, the time for heating the ferroelectric film can be made shorter.

[0046] The semiconductor device to which the present invention isapplied may include, e.g., non-volatile semiconductor memories andlarge-capacity DRAMs. The ferroelectric film in the semiconductor devicemay be any of films comprised of a dielectric material having a highdielectric constant, and may include, e.g., ferroelectric materialshaving a perovskite crystalline structure.

[0047] The dielectric material may include lead titanate zirconatePb(Zr,Ti)O₃ (abbreviated “PZT”), barium strontium titanate (Ba,Sr)TiO₃(abbreviated “BST”), and niobium strontium bismuth tantalate(SrBi₂(Nb,Ta)₂O₉ (called “Y1 system”). These materials can be formedinto films by chemical vapor deposition (CVD), the sol-gel method, orsputtering.

[0048] An example of the resin-encapsulated semiconductor apparatus ofthe present invention will be described below, taking as an example alead-on-chip type (“LOC type”) resin-encapsulated semiconductorapparatus shown in FIG. 1. The resin-encapsulated semiconductorapparatus is by no means limited to the LOC type, and may be adifferent-type resin-encapsulated semiconductor apparatus such as achip-on-lead type (“COL type”).

[0049] The resin-encapsulated semiconductor apparatus of the presentinvention has a semiconductor device 1 having on at least part of itssurface a surface-protective film 2 comprised of polyimide; an outerterminal 3; an adhesive member 4 which bonds the semiconductor device 1and the outer terminal 3 through the surface-protective film 2; wiring 5for achieving conduction between the semiconductor device 1 and theouter terminal 3; and a encapsulant medium 6 for encapsulating theentire semiconductor device 1 and wiring 5. The surface-protective film2 is comprised of a polyimide obtained by heat-curing the polyimideprecursor previously described. In the resin-encapsulated semiconductorapparatus shown in FIG. 1, the outer terminal 3 also serves as a leadframe.

[0050] An example of the process for fabricating the resin-encapsulatedsemiconductor apparatus of the present invention will be described belowwith reference to FIGS. 2A to 2F. FIGS. 2A to 2F show a process forfabricating the LOC type resin-encapsulated semiconductor apparatusshown in FIG. 1. The fabrication process of the present invention is notlimited to the fabrication of the LOC type resin-encapulatedsemiconductor apparatus, and may also be applied to the fabrication ofthe resin-encapsulated semiconductor apparatuses of the other type suchas COL type so long as they are resin-encapsulated semiconductorapparatuses obtained by previously bonding semiconductor devices andouter terminals (lead frames) and then encapsulating them with a moldingresin.

[0051] (1) Surface-protective Film Forming Step:

[0052] As shown in FIG. 2A, a surface-protective film 2 comprised ofpolyimide is formed on a silicon wafer 9 on which semiconductor deviceregions and wiring layers (not shown) have been built up. Thesurface-protective film 2 may be formed by, e.g., a method in which thepolyimide precursor composition previously described is coated on thewafer 9, followed by heat curing, and a method in which the polyimideprecursor composition previously molded in a filmy form is placed on thesurface of the wafer 9, followed by heat curing.

[0053] As previously described, in the surface-protective film 2,openings are formed at predetermined positions, and the surface of thesemiconductor device 1 is laid bare at the areas of bonding pad portions7 and scribing regions 8. To form the surface-protective film 2 in apattern with openings corresponding to the bonding pad areas 7 andscribing regions 8, wet etching may be used which is a method making useof a photoresist and a polyimide etching solution, and besides aphoto-etching technique such as dry etching in which a patternedinorganic film or metal film is used as a mask and the polyimide filmlaid bare is removed by oxygen plasma. Alternatively, using a mask, thepolyimide precursor composition may be coated except at the portions ofthe regions 7 and 8, and thus the surface-protective film 2 can bepatterned.

[0054] The silicon wafer 9 on which the surface-protective film 2 hasbeen formed in this way is cut off at its scribing regions to obtain thesemiconductor device 1 (shown in FIG. 2B) having the surface-protectivefilm 2. Here, a process is described in which the silicon wafer 9 withthe surface-protective film 2 having been formed thereon is cut off toobtain the semiconductor device 1 having the surface-protective film 2.In the present invention, without limitation thereto, the silicon wafer9 may be cut off to obtain a semiconductor device 1 and thereafter thefilm of the polyimide precursor composition may be formed on the surfaceof the semiconductor device 1 thus obtained, followed by heat curing toobtain the semiconductor device 1 having the surface-protective film 2.

[0055] (2) Device Mounting Step:

[0056] The outer terminal 3 and the semiconductor device 1 are bondedthrough an adhesive member 4 to obtain an assembly comprised of, asshown in FIG. 2C, the semiconductor device 1 and the outer terminal 3which are bonded through the surface-protective film 2 and the adhesivemember 4. Subsequently, as shown in FIG. 2D, the semiconductor device 1is wired with gold wires 5 across its bonding pad areas 7 and outerterminals 3 by means of a wire bonder to ensure the conduction betweenthe semiconductor device 1 and the outer terminals 3.

[0057] (3) Sealing Step:

[0058] As shown in FIG. 2E, molding is applied using a silica-containingepoxy resin at a molding temperature of 180° C. and a molding pressureof 70 kg/cm² to form an encapsulant member 6. Finally, the outerterminals 3 are bent into the desired shape, to thus obtain the LOC typeresin-encapsulated semiconductor apparatus as shown in FIG. 2F.

[0059] The semiconductor device used in the resin-encapsulatedsemiconductor apparatus of the present invention will be describedbelow. As an example of the semiconductor device used in theresin-encapsulated semiconductor apparatus of the present invention, aferroelectric memory comprising a memory cell of one transistor/onecapacitor is shown in FIG. 4 as a cross-section at its memory cellportion.

[0060] This ferroelectric memory, 40, is a laminate comprising a siliconsubstrate 41; formed on its surface, a CMOS (complementary metal oxidesemiconductor) transistor layer 42 consisting of a p- or n-type well421, a set of source 422 and drain 423, an oxide film 424, a gate 425and an insulating layer 426, and further formed on the surface of theinsulating layer 426 a capacitor 43 consisting of a lower electrodelayer 431, a ferroelectric film 432, an upper electrode layer 433, ametal wiring layer 434 and an insulating layer 435. Thus, the presentinvention is applied to the instance where the surface-protectivepolyimide film is formed on the surface of the laminate (inclusive ofthe semiconductor device) having the ferroelectric film 432 andthereafter the assembly formed is encapsulated with resin. In theexample shown in FIG. 4, the surface-protective polyimide film is soformed as to cover the metal wiring layer 434 and insulating layer 435of the capacitor 43.

[0061] As described above in detail, the resin-encapsulatedferroelectric device having the surface-protective polyimide film isprovided by the present invention. Since the polyimide precursor isheat-cured at a temperature of from 230° C. to 300° C., theferroelectric film may cause less deterioration of polarizationcharacteristics. Also, since the polyimide constituting thesurface-protective film 2 has a glass transition temperature of 240° C.or above and a Young's modulus of 2,600 MPa or above, aresin-encapsulated semiconductor apparatus can be obtained which has asuperior solder reflow resistance after being resin encapsulating and inwhich no peeling may occur at the interface between the polyimide andthe encapsulant resin at the time of refloing solder. Also, since thepolyimide precursor composition is used which is heat-cured at atemperature higher than 300° C. but not higher than 350° C. for aheating time within 4 minutes and also the polyimide obtained aftercuring of which has a glass transition temperature of 260° C. or aboveand a Young's modulus of 3,500 MPa or above, it is possible to obtain aresin-encapsulated semiconductor apparatus that may cause lessdeterioration of polarization characteristics of the ferroelectric filmand has a superior solder reflow resistance after resin encapsulatingand in which no peeling may occur at the interface between the polyimideand the sealing resin at the time of reflowing solder. Thus, accordingto the present invention, a resin-encapsulated semiconductor apparatuswith a high reliability can be obtained.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0062] Examples of the present invention will be given below.

[0063] With respect to polyimide films used in the following Examples,the Young's modulus and the glass transition temperature were measuredusing polyimide films separately prepared. More specifically, first,using a hot plate, a polyimide film was formed on a silicon wafer underthe same conditions as in each Example, and thereafter the polyimidefilm was peeled off the wafer, followed by washing with water and thendrying to obtain a polyimide film with a layer thickness of from 9 to 10μm. This polyimide film was cut to make a test piece 25 mm long×5 mmwide. Using a tensile tester AUTOGRAPH AG-100E (manufactured by ShimadzuCorporation), tensile load and elongation with respect to the film weremeasured under conditions of a rate of pulling of 1 mm/minute todetermine the Young's modulus. The polyimide film was also cut in 15 mmlong×5 mm wide to make a test piece. At a load of 2 g/f (about 4×10⁻²N/m²) in the elongation direction and a rate of temperature rise of 5°C./minutes, a thermal expansion curve obtained from thermomechanicalmeasurement using TA-1500 (manufactured by Shinku Riko ULVAC) wasprepared, and from this curve the glass transition temperature wasdetermined.

[0064] The solder reflow resistance of the resin-encapsulatedsemiconductor apparatus was measured in the following way. First, theresin-encapsulated semiconductor apparatus was moistened by leaving itfor 168 hours under thermostatic hygrostatic conditions of 85° C. and85%. The resin-encapsulated semiconductor apparatus thus moistened washeated to a maximum temperature of 240 to 250° C. for 10 seconds andthen left to cool to room temperature, and this step was repeatedlycarried out three times. Thereafter, using an ultrasonic flaw detector,any interfacial failure between the polyimide and the encapsulant resinwas non-destructively observed to examine the solder reflow resistanceof the surface-protective polyimide film. With regard to the temperatureprofile of an infrared solder reflowing furnace, the temperature profiledescribed in “Packaging Techniques for Surface Mount Type LSI Packagesand Improvement in Its Reliability”, p.451 (compiled by Hitachi Ltd.,Semiconductor Integrated Circuits Division, published 1988) wasfollowed, setting a maximum temperature at 240 to 245° C.

[0065] Viscosity of polyimide precursor solutions was measured at 25° C.using a viscometer Model DVR-E (manufactured by K.K. Tokimec).

EXAMPLE 1

[0066] In a stream of nitrogen, 92.0 g (0.46 mol) of4,4′-diaminodiphenyl ether and 9.12 g (0.44 mol) of 4-aminophenyl4-amino-3-carbonamidophenyl ether were dissolved in 1,580.2 g ofN-methyl-2-pyrrolidone to prepare an amine solution. Next, keeping thetemperature of this solution at about 15° C., a mixture of 54.5 g (0.25mol) of pyromellitic dianhydride and 80.5 g (0.25 mol) of3,3′,4,4′-benzophenonetetracarboxylic dianhydride was added whilestirring. After their addition was completed, the reaction mixture wasfurther reacted while stirring at about 15° C. for about 5 hours in anatmosphere of nitrogen, to obtain a polyimide precursor compositionsolution with a viscosity of about 30 poises. The polyimide precursorcomposition solution thus obtained contains as the polyimide precursorthe polyamic acid represented by the following general formula (I).

[0067] Here, the polyamide acid of the present Example is a copolymerwherein R¹ is

[0068] In the formulas (I) and (II), the numerals in brackets indicatethe ratio of the numbers of repeating units in one molecule.

[0069] A wafer was prepared on which a semiconductor device comprising acapacitive insulation film formed using a ferroelectric material, asilicon nitride film formed on the outermost surface, and bonding padsfor ensuring conduction were formed.

[0070] On this wafer, a PIQ coupler available from Hitachi Chemical Co.,Ltd. was spin-coated, followed by heating at 300° C. for 4 minutes inthe air using a hot-plate heating unit, and thereafter the abovepolyimide precursor composition solution was further spin-coatedthereon, followed by heating at 140° C. for 1 minute in an atmosphere ofnitrogen using the hot-plate heating unit.

[0071] Next, a positive photoresist OFPR800, available from Tokyo OhkaKogyo Co., Ltd., was spin-coated thereon, followed by heating at 90° C.for 1 minute using the hot-plate heating unit to form a resist film onthe surface of the polyimide precursor composition film. The resist filmformed was then exposed through a photomask and developed to form in theresist film the openings where the underlying polyimide precursor filmwas laid bare, followed by heating at 160° C. for 1 minute using thehot-plate heating unit.

[0072] Next, using the resist developing solution aqueous alkalisolution as it was, the polyimide precursor composition film was etchedto form openings in the polyimide precursor composition film at itsportions corresponding to the resist openings. Then the resist film wasremoved using a resist removing solution and a rinsing solution forexclusive use, and the polyimide precursor composition film was washedwith water, followed by heating at 230° C. for 4 minutes and at 300° C.for 8 hours to make the polyimide precursor into an imide to form on thedevice surface a surface-protective polyimide film having openings atthe bonding pad portions. The polyimide film thus formed was in a layerthickness of 2.3 μm. The Young's modulus and glass transitiontemperature of the polyimide film were measured in the manner asdescribed above, to reveal that they were about 3,700 MPa and about 300°C., respectively.

[0073] Thereafter, using the polyimide film as a mask, the siliconnitride film covering the bonding pad portions was dry-etched with amixed gas of 94% CF₄ and 6% O₂ to lay the aluminum electrode bare at thebonding pad portions.

[0074] At this stage, as electrical characteristics of the device, therate of residual polarization of the ferroelectric film was measured tofind that it was in a value only decreased by 5% compared with the rateof residual polarization of the initial ferroelectric film before thePIQ coupler treatment.

[0075] Next, this wafer with films thus processed was cut off at thescribing regions to obtain a semiconductor device having thesurface-protective film. This semiconductor device was secured to a leadframe in the step of die bonding, and thereafter the semiconductordevice was wired with gold wires across the bonding pad portions andouter terminals. The device thus wired was further encapsulated with asilica-containing biphenyl type epoxy resin available from HitachiChemical Co., Ltd. at a molding temperature of 180° C. and a moldingpressure of 70 kg/cm² to form a resin-encapsulated portion. Finally, theouter terminals were bent into the predetermined shape to obtain afinished product of the resin-encapsulated semiconductor apparatus shownin FIG. 3.

[0076] The resin-encapsulated semiconductor apparatus thus obtained wastested to evaluate the solder reflow resistance in the manner asdescribed above. As a result, neither peeling nor cracks occurred at theinterface between the surface-protective polyimide film and theencapsulant epoxy resin, thus a resin-encapsulated semiconductorapparatus with a high reliability was obtainable.

Comparative Example 1

[0077] The same wafer as that in Example 1 was prepared, and on thiswafer with the semiconductor device a PIQ coupler available from HitachiChemical Co., Ltd. was spin-coated, followed by heating at 300° C. for 4minutes in the air using a hot-plate heating unit, and thereafter apolyimide precursor solution PIQ-13, available from Hitachi ChemicalCo., Ltd., was spin-coated thereon, followed by heating at 140° C. for 1minute in an atmosphere of nitrogen using the hot-plate heating unit, toform a polyimide precursor composition film.

[0078] Next, openings were formed in the polyimide precursor compositionfilm in the same manner as in Example 1, followed by heating at 230° C.for 4 minutes in an atmosphere of nitrogen using the hot-plate heatingunit and further followed by heating at 350° C. for 30 minutes in anatmosphere of nitrogen using a lateral type diffusion furnace. Thus, apolyimide film (PIQ-13 film) having openings at the bonding pad portionswas formed on the device surface. The PIQ-13 film thus formed was in alayer thickness of 2.3 μm. The Young's modulus and glass transitiontemperature of the PIQ-13 film were measured in the manner as describedabove, to reveal that they were about 3,300 MPa and about 310° C.,respectively.

[0079] Thereafter, in the same manner as in Example 1, the aluminumelectrode was laid bare at the bonding pad portions and the rate ofresidual polarization of the ferroelectric film was measured to findthat it was in a value decreased by 60% compared with the value beforethe PIQ coupler treatment.

[0080] Next, a finished product of a resin-encapsulated semiconductorapparatus was produced in the same manner as in Example 1, and itssolder reflow resistance was evaluated in the same manner as inExample 1. As a result, neither peeling nor cracks occurred at theinterface between the surface-protective polyimide film and theencapsulant epoxy resin, but, compared with the device of Example 1, theresin-encapsulated semiconductor apparatus obtained in the presentComparative Example caused so great a deterioration in polarizationcharacteristics of the ferroelectric film that it was unsuitable forpractical use.

Comparative Example 2

[0081] A surface-protective film was formed on the surface of the waferwith the semiconductor device in the same manner as Comparative Example1 except that the heating time for the heat-curing of the polyimideprecursor composition film at 350° C. was shortened to 8 minutes. TheYoung's modulus and glass transition temperature of the PIQ-13 film inthe present Comparative Example were, like those in Comparative Example1, about 3,300 MPa and about 310° C., respectively. However, the rate ofresidual polarization of the ferroelectric film was in a value decreasedby 25% compared with the value before the PIQ coupler treatment, and,compared with the device of Example 1, the present device caused sogreat a deterioration in polarization characteristics that it wasunsuitable for practical use.

Comparative Example 3

[0082] The same wafer as that in Example 1 was prepared, and on thiswafer with the semiconductor device a polyimide precursor compositionPIX8803-9L, available from Hitachi Chemical Co., Ltd., was spin-coated,followed by heating at 100° C. for 1 minute and further at 230° C. for 8minutes in an atmosphere of nitrogen using a hot-plate heating unit, toform a polyimide precursor composition film in a half-cured state.

[0083] Next, openings were formed in this polyimide precursorcomposition film in the same manner as in Example 1, followed by heatingat 230° C. for 4 minutes in an atmosphere of nitrogen using thehot-plate heating unit to form a polyimide film (PIX8803-9L film) havingopenings at the bonding pad portions. The polyimide film thus formed wasin a layer thickness of 2.3 μm. The Young's modulus and glass transitiontemperature of the PIX8803-9L film were measured in the manner asdescribed above, to reveal that they were about 2,000 MPa and about 200°C., respectively.

[0084] Next, using the polyimide film as a mask, the silicon nitridefilm was dry-etched in the same manner as in Example 1 to lay thealuminum electrode bare at the bonding pad portions, and the rate ofresidual polarization of the ferroelectric film was measured to findthat the difference between the value obtained and the value before thecoating of the polyimide precursor composition was within 1%, showingalmost no deterioration of characteristics.

[0085] Next, a finished product of a resin-encapsulated semiconductorapparatus was produced in the same manner as in Example 1, and itssolder reflow resistance was evaluated in the same manner as inExample 1. As a result, peeling was seen to occur over the wholeinterface between the surface-protective polyimide film and theencapsulant epoxy resin, and only a resin-encapsulated semiconductorapparatus with an extremely low reliability was obtainable.

EXAMPLE 2

[0086] In a stream of nitrogen, 88.0 g (0.44 mol) of4,4′-diaminodiphenyl ether and 13.68 g (0.06 mol) of 4-aminophenyl4-amino-3-carbonamidophenyl ether were dissolved in 1,584 g ofN-methyl-2-pyrrolidone to prepare an amine solution. Next, keeping thetemperature of this solution at about 15° C., a mixture of 54.5 g (0.25mol) of pyromellitic dianhydride and 80.5 g (0.25 mol) of3,3′,4,4′-benzophenonetetracarboxylic dianhydride was added whilestirring. After their addition was completed, the mixture was furtherreacted while stirring at about 15° C. for about 5 hours in anatmosphere of nitrogen, to obtain a polyimide precursor compositionsolution with a viscosity of about 30 poises. The polyimide precursorcomposition solution thus obtained contains as the polyimide precursorthe same polyamic acid copolymer as that of Example 1 except that R² isin a different copolymerization ratio. The R² in the present Example is

[0087] In the formula (XIII), the numeral in brackets indicates theratio of the numbers of repeating units in one molecule.

[0088] Next, the same wafer as that in Example 1 was prepared, and onthe surface of this wafer with the semiconductor device a PIQ coupleravailable from Hitachi Chemical Co., Ltd. was spin-coated, followed byheating at 260° C. for 4 minutes in the air using a hot-plate heatingunit, and thereafter the above polyimide precursor composition solutionwas further spin-coated thereon, followed by heating at 140° C. for 1minute in an atmosphere of nitrogen using the hot-plate heating unit.Thus, a polyimide precursor composition film was formed.

[0089] Openings were provided in this composition film in the samemanner as in Example 1, followed by heating at 230° C. for 4 minutes andat 260° C. for 8 hours to make the polyimide precursor into an imide toform on the device surface a surface-protective polyimide film havingopenings at the bonding pad portions. The polyimide film thus formed wasin a layer thickness of 2.3 μm. The Young's modulus and glass transitiontemperature of the polyimide film were measured in the manner asdescribed above, to reveal that they were about 3,300 MPa and about 300°C., respectively.

[0090] At this stage, the rate of residual polarization of theferroelectric film was measured to find that it was in a value onlydecreased by about 2% compared with the rate of residual polarization ofthe initial ferroelectric film before the PIQ coupler treatment.

[0091] Next, a finished product of a resin-encapsulated semiconductorapparatus was produced in the same manner as in Example 1, and thefinished product thus obtained was tested to evaluate the solder reflowresistance. As a result, neither peeling nor cracks occurred at theinterface between the surface-protective polyimide film and theencapsulant epoxy resin, thus a resin-encapsulated semiconductorapparatus with a high reliability was obtainable.

EXAMPLE 3

[0092] In a stream of nitrogen, 90.0 g (0.45 mol) of4,4′-diaminodiphenyl ether and 9.6 g (0.05 mol) ofbis(3-aminopropyl)tetramethyldisiloxane were dissolved in 1,584 g ofN-methyl-2-pyrrolidone to prepare an amine solution. Next, keeping thetemperature of this solution at about 15° C., 147 g (0.5 mol) of3,3′,4,4′-biphenyltetracarboxylic dianhydride was added while stirring.After its addition was completed, the reaction mixture was furtherreacted while stirring at about 15° C. for about 5 hours in anatmosphere of nitrogen, to obtain a polyimide precursor compositionsolution with a viscosity of about 50 poises. The polyimide precursorcomposition solution thus obtained contains as the polyimide precursor apolyamic acid copolymer comprised of a first repeating unit representedby the following general formula (XIV) and a second repeating unitrepresented by the following general formula (XV). Here, the proportionof the number of the second repeating unit to the total number of thefirst repeating unit and second repeating unit is 10%.

[0093] Next, the same wafer as that in Example 1 was prepared, and onthe surface of this wafer with the semiconductor device a PIQ coupleravailable from Hitachi Chemical Co., Ltd. was spin-coated, followed byheating at 260° C. for 4 minutes in the air using a hot-plate heatingunit, and thereafter the above polyimide precursor composition solutionwas further spin-coated thereon, followed by heating at 140° C. for 1minute in an atmosphere of nitrogen using the hot-plate heating unit.Thus, a polyimide precursor composition film was formed.

[0094] Openings were provided in this composition film in the samemanner as in Example 1, followed by heating at 230° C. for 4 minutes andat 260° C. for 8 minutes to make the polyimide precursor into an imideto form on the device surface a surface-protective polyimide film havingopenings at the bonding pad portions. The polyimide film thus formed wasin a layer thickness of 2.3 μm. The Young's modulus and glass transitiontemperature of the polyimide film were measured in the manner asdescribed above, to reveal that they were about 3,000 MPa and about 255°C., respectively.

[0095] At this stage, the rate of residual polarization of theferroelectric film was measured to find that it was in a value onlydecreased by about 2% compared with the rate of residual polarization ofthe initial ferroelectric film before the PIQ coupler treatment.

[0096] Next, a finished product of a resin-encapsulated semiconductorapparatus was produced in the same manner as in Example 1, and thefinished product thus obtained was tested to evaluate the solder reflowresistance. As a result, neither peeling nor cracks occurred at theinterface between the surface-protective polyimide film and the sealingepoxy resin, thus a resin-encapsulated semiconductor apparatus with ahigh reliability was obtainable.

EXAMPLE 4

[0097] In a stream of nitrogen, 103.0 g (0.5 mol) of3,3′-dimethylbenzidine was dissolved in 1,474.5 g ofN-methyl-2-pyrrolidone, and 155.0 g (0.5 mol) of 4,4′-oxyphthalicdianhydride was added while stirring. After its addition was completed,the reaction mixture was further reacted while stirring at about 15° C.for about 5 hours in an atmosphere of nitrogen, to obtain a polyimideprecursor composition solution with a viscosity of about 30 poises. Thepolyimide precursor composition solution thus obtained contains as thepolyimide precursor a polyamide acid comprised of a repeating unitrepresented by the following general formula (XVI):

[0098] Next, the same wafer as that in Example 1 was prepared, and onthe surface of this wafer with the semiconductor device a PIQ coupleravailable from Hitachi Chemical Co., Ltd. was spin-coated, followed byheating at 240° C. for 4 minutes in the air using a hot-plate heatingunit, and thereafter the above polyimide precursor composition solutionwas further spin-coated thereon, followed by heating at 140° C. for 1minute in an atmosphere of nitrogen using the hot-plate heating unit.Thus, a polyimide precursor composition film was formed.

[0099] Openings were provided in this composition film in the samemanner as in Example 1, followed by heating at 230° C. for 4 minutes andat 240° C. for 10 minutes to make the polyimide precursor into an imideto form on the device surface a surface-protective polyimide film havingopenings at the bonding pad portions. The polyimide film thus formed wasin a layer thickness of 2.3 μm. The Young's modulus and glass transitiontemperature of the polyimide film were measured in the manner asdescribed above, to reveal that they were about 4,000 MPa and about 250°C., respectively.

[0100] At this stage, the rate of residual polarization of theferroelectric film was measured to find that it was in a value decreasedby about 1% at most, compared with the rate of residual polarization ofthe initial ferroelectric film before the PIQ coupler treatment.

[0101] Next, a finished product of a resin-encapsulated semiconductorapparatus was produced in the same manner as in Example 1, and thefinished product thus obtained was tested to evaluate the solder reflowresistance. As a result, neither peeling nor cracks occurred at theinterface between the surface-protective polyimide film and theencapsulant epoxy resin, thus a resin-encapsulated semiconductorapparatus with a high reliability was obtainable.

EXAMPLE 5

[0102] In the polyimide precursor composition solution synthesized inExample 1, 20.0 parts by weight of 3-(N,N-dimethylamino)propylmethacrylate and 5.0 parts by weight of2,6-di(p-azidobenzal)-4-carboxycyclohexanone based on 100 parts byweight of the polyimide precursor polymer were added and dissolved toobtain a photosensitive composition solution.

[0103] Next, the same wafer as that in Example 1 was prepared, and onthe surface of this wafer with the semiconductor device a PIQ coupleravailable from Hitachi Chemical Co., Ltd. was spin-coated, followed byheating at 250° C. for 4 minutes in the air using a hot-plate heatingunit, and thereafter the above photosensitive composition solution wasfurther spin-coated thereon, followed by heating at 85° C. for 1 minuteand subsequently at 95° C. for 1 minute in an atmosphere of nitrogenusing a hot-plate heating unit. Thus, a polyimide precursor compositionfilm was formed.

[0104] This composition film was exposed through a photomask and thendeveloped with a mixture solution comprised of 4 parts by volume ofN-methyl-2-pyrrolidone and 1 part by volume of ethanol, followed byrinsing with ethanol to form openings at the bonding pad portions. Next,the film was heated successively at 130° C. for 4 minutes, at 170° C.for 4 minutes, at 220° C. for 4 minutes and at 250° C. for 8 minutesusing the hot-plate heating unit to cause the polyimide precursor tocure to form a polyimide film having openings at the bonding padportions. The polyimide film thus formed was in a layer thickness of 2.3μm. The Young's modulus and glass transition temperature of thepolyimide film were also measured to reveal that they were about 3,300MPa and about 300° C., respectively.

[0105] At this stage, the rate of residual polarization of theferroelectric film was measured to find that it was in a value decreasedby about 1% at most, compared with the rate of residual polarization ofthe initial ferroelectric film before the PIQ coupler treatment.

[0106] Next, a finished product of a resin-encapsulated semiconductorapparatus was produced in the same manner as in Example 1, and thefinished product thus obtained was tested to evaluate the solder reflowresistance. As a result, neither peeling nor cracks occurred at theinterface between the surface-protective polyimide film and theencapsulant epoxy resin, thus a resin-encapsulated semiconductorapparatus with a high reliability was obtainable.

EXAMPLE 6

[0107] In the polyimide precursor composition solution synthesized inExample 2, 20.0 parts by weight of 3-(N,N-dimethylamino)propylmethacrylate, 3.0 parts by weight of Michler's ketone and 3.0 parts byweight of bis-4,4′-diethylaminobenzophenone based on 100 parts by weightof the polyimide precursor polymer were added and dissolved to obtain aphotosensitive composition solution.

[0108] Next, the same wafer as that in Example 1 was prepared, and onthe surface of this wafer with the semiconductor device a PIQ coupleravailable from Hitachi Chemical Co., Ltd. was spin-coated, followed byheating at 270° C. for 4 minutes in the air using a hot-plate heatingunit, and thereafter the above photosensitive composition solution wasfurther spin-coated thereon, followed by heating at 85° C. for 1 minuteand subsequently at 95° C. for 1 minute in an atmosphere of nitrogenusing a hot-plate heating unit. Thus, a polyimide precursor compositionfilm was formed.

[0109] Openings were formed in this composition film in the same manneras in Example 5, followed by heating successively at 130° C. for 4minutes, at 170° C. for 4 minutes, at 220° C. for 4 minutes and at 270°C. for 8 minutes using the hot-plate heating unit to cause the polyimideprecursor to cure to form a polyimide film having openings at thebonding pad portions. The polyimide film thus formed was in a layerthickness of 2.3 μm. The Young's modulus and glass transitiontemperature of the polyimide film were also measured to reveal that theywere about 3,300 MPa and about 300° C., respectively.

[0110] At this stage, the rate of residual polarization of theferroelectric film was measured to find that it was in a value decreasedby about 1% at most, compared with the rate of residual polarization ofthe initial ferroelectric film before the PIQ coupler treatment.

[0111] Next, a finished product of a resin-encapsulated semiconductorapparatus was produced in the same manner as in Example 1, and thefinished product thus obtained was tested to evaluate the solder reflowresistance. As a result, neither peeling nor cracks occurred at theinterface between the surface-protective polyimide film and theencapsulant epoxy resin, thus a resin-encapsulated semiconductorapparatus with a high reliability was obtainable.

EXAMPLE 7

[0112] In the polyimide precursor composition solution synthesized inExample 3, 20.0 parts by weight of 3-(N,N-dimethylamino)propylmethacrylate and 5.0 parts by weight of2,6-di(p-azidobezal)-4-carboxycyclohexanone based on 100 parts by weightof the polyimide precursor polymer were added and dissolved to obtain aphotosensitive composition solution.

[0113] Next, the same wafer as that in Example 1 was prepared, and onthe surface of this wafer with the semiconductor device a PIQ coupleravailable from Hitachi Chemical Co., Ltd. was spin-coated, followed byheating at 260° C. for 4 minutes in the air using a hot-plate heatingunit, and thereafter the above photosensitive composition solution wasfurther spin-coated thereon, followed by heating at 85° C. for 1 minuteand subsequently at 95° C. for 1 minute in an atmosphere of nitrogenusing a hot-plate heating unit. Thus, a polyimide precursor compositionfilm was formed.

[0114] Openings were formed in this composition film in the same manneras in Example 5, followed by heating successively at 130° C. for 4minutes, at 170° C. for 4 minutes, at 220° C. for 4 minutes and at 260°C. for 8 minutes using the hot-plate heating unit to cause the polyimideprecursor to cure to form a polyimide film having openings at thebonding pad portions. The polyimide film thus formed was in a layerthickness of 2.3 μm. The Young's modulus and glass transitiontemperature of the polyimide film were also measured to reveal that theywere about 3,000 MPa and about 260° C., respectively.

[0115] At this stage, the rate of residual polarization of theferroelectric film was measured to find that it was in a value decreasedby about 2% at most, compared with the rate of residual polarization ofthe initial ferroelectric film before the PIQ coupler treatment.

[0116] Next, a finished product of a resin-encapsulated semiconductorapparatus was produced in the same manner as in Example 1, and thefinished product thus obtained was tested to evaluate the solder reflowresistance. As a result, neither peeling nor cracks occurred at theinterface between the surface-protective polyimide film and theencapsulant epoxy resin, thus a resin-encapsulated semiconductorapparatus with a high reliability was obtainable.

EXAMPLE 8

[0117] In the polyimide precursor composition solution synthesized inExample 4, 20.0 parts by weight of 3-(N,N-dimethylamino)propylmethacrylate, 3.0 parts by weight of Michler's ketone and 3.0 parts byweight of bis-4,4′-diethylaminobenzophenone based on 100 parts by weightof the polyimide precursor polymer were added and dissolved to obtain aphotosensitive composition solution.

[0118] Next, the same wafer as that in Example 1 was prepared, and thesurface of this wafer with the semiconductor device was treated with thePIQ coupler in the same manner as in Example 5, and thereafter the abovephotosensitive composition solution was further spin-coated thereonfollowed by heating, in the same manner as in Example 5. Thus, apolyimide precursor composition film was formed.

[0119] Openings were formed in this composition film in the same manneras in Example 5, and the film was heat-cured in the same manner as inExample 5 to form a polyimide film. The polyimide film thus formed wasin a layer thickness of 2.3 μm. The Young's modulus and glass transitiontemperature of the polyimide film were measured to reveal that they wereabout 4,000 MPa and about 250° C., respectively.

[0120] At this stage, the rate of residual polarization of theferroelectric film was measured to find that it was in a value decreasedby about 1% at most, compared with the rate of residual polarization ofthe initial ferroelectric film before the PIQ coupler treatment.

[0121] Next, a finished product of a resin-encapsulated semiconductorapparatus was produced in the same manner as in Example 1, and thefinished product thus obtained was tested to evaluate the solder reflowresistance. As a result, neither peeling nor cracks occurred at theinterface between the surface-protective polyimide film and theencapsulant epoxy resin, thus a resin-encapsulated semiconductorapparatus with a high reliability was obtainable.

EXAMPLE 9

[0122] The same wafer as that in Example 1 was prepared, and on thesurface of this wafer with the semiconductor device a PIQ coupleravailable from Hitachi Chemical Co., Ltd. was spin-coated, followed byheating at 230° C. for 4 minutes in the air using a hot-plate heatingunit, and thereafter the polyimide precursor composition solutionsynthesized in Example 4 was further spin-coated thereon, followed byheating at 140° C. for 1 minute in an atmosphere of nitrogen using ahot-plate heating unit. Thus, a polyimide precursor composition film wasformed.

[0123] Openings were formed in this composition film in the same manneras in Example 4, followed by heating at 200° C. for 4 minutes andsubsequently at 230° C. for 10 minutes using the hot-plate heating unitto cause the polyimide precursor to cure to form a surface-protectivepolyimide film having openings at the bonding pad portions. Thepolyimide film thus formed was in a layer thickness of 2.3 μm. TheYoung's modulus and glass transition temperature of the polyimide filmwere also measured to reveal that they were about 4,000 MPa and about250° C., respectively.

[0124] At this stage, the rate of residual polarization of theferroelectric film was measured to find that, like Example 4, thedeterioration due to heat treatment was about 1% at most. A finishedproduct of a resin-encapsulated semiconductor apparatus was produced inthe same manner as in Example 1, and the finished product thus obtainedhad a solder reflow resistance as good as that in Example 4.

EXAMPLE 10

[0125] In the polyimide precursor composition solution synthesized inExample 4, 20.0 parts by weight of 3-(N,N-dimethylamino)propylmethacrylate and 6.0 parts by weight of Michler's ketone based on 100parts by weight of the polyimide precursor polymer were added anddissolved to obtain a photosensitive composition solution.

[0126] Next, the same wafer as that in Example 1 was prepared, and thesurface of this wafer with the semiconductor device was treated with thePIQ coupler in the same manner as in Example 9, and thereafter the abovephotosensitive composition solution was further spin-coated thereon,followed by heating at 85° C. for 1 minute and subsequently at 95° C.for 1 minute in an atmosphere of nitrogen using a hot-plate heatingunit. Thus, a polyimide precursor composition film was formed.

[0127] Openings were formed in this composition film in the same manneras in Example 5, followed by heating successively at 130° C. for 4minutes, at 170° C. for 4 minutes, at 200° C. for 4 minutes and at 230°C. for 10 minutes using the hot-plate heating unit to cause thepolyimide precursor to cure to form a polyimide film having openings atthe bonding pad portions. The polyimide film thus formed was in a layerthickness of 2.3 μm. The Young's modulus and glass transitiontemperature of the polyimide film were also measured to reveal that theywere about 4,000 MPa and about 250° C., respectively.

[0128] At this stage, the rate of residual polarization of theferroelectric film was measured to find that, like Example 4, thedeterioration due to heat treatment was about 1% at most. A finishedproduct of a resin-encapsulated semiconductor apparatus was produced inthe same manner as in Example 1, and the finished product thus obtainedhad a solder reflow resistance as good as that in Example 4.

EXAMPLE 11

[0129] In a stream of nitrogen, 95.4 g (0.45 mol) of3,3′-dimethylbenzidine and 9.6 g (0.05 mol) ofbis(3-aminopropyl)tetramethyldisiloxane were dissolved in 1,040 g ofN-methyl-2-pyrrolidone to prepare an amine solution. Next, keeping thetemperature of this solution at about 15° C., 155.0 g (0.5 mol) of4,4′-oxyphthalic dianhydride was added while stirring, and thereafterthe reaction mixture was further stirred at about 15° C. for about 8hours in an atmosphere of nitrogen, to obtain a polyimide precursorsolution with a viscosity of about 30 poises.

[0130] The polyimide precursor composition solution thus obtainedcontains as the polyimide precursor a polyamic acid copolymer comprisedof a first repeating unit represented by the above general formula (XVI)and a second repeating unit represented by the following general formula(XIX):

[0131] Here, the number of the second repeating unit comprised about 10%of the whole. Using the polyimide precursor solution thus obtained, aphotosensitive composition solution was prepared in the same manner asin Example 5.

[0132] Next, the same wafer as that in Example 1 was prepared, and onthe surface of this wafer the photosensitive composition solution wasspin-coated, followed by heating at 85° C. for 1 minute and subsequentlyat 95° C. for 1 minute in an atmosphere of nitrogen using a hot-plateheating unit. Thereafter, the composition film formed was exposedthrough a photomask and then developed with a mixture solution comprisedof 4 parts by volume of N-methyl-2-pyrrolidone and 1 part by volume ofethanol, followed by rinsing with ethanol to form openings where thebonding pad portions were uncovered. Subsequently, the film was heatedsuccessively at 130° C. for 3 minutes, at 170° C. for 3 minutes, at 220°C. for 3 minutes and at 300° C. for 6 minutes using the hot-plateheating unit to cause the polyimide precursor to cure. The polyimidefilm thus formed was in a layer thickness of 2.3 μm. The Young's modulusand glass transition temperature of the polyimide film were about 4,000MPa and about 260° C., respectively.

[0133] At this stage, the rate of residual polarization of theferroelectric film was measured to find that it was in a value decreasedby about 1% at most, compared with the rate of residual polarization ofthe initial ferroelectric film before the coating of the polyimideprecursor solution.

[0134] Next, a finished product of a resin-encapsulated semiconductorapparatus was produced in the same manner as in Example 1, andthereafter was tested to evaluate the solder reflow resistance in thesame manner as in Example 1. As a result, like Example 1, the producthad a high reliability.

EXAMPLE 12

[0135] In the present Example, a resin-encapsulated semiconductorapparatus was fabricated in the same manner as in Example 11 except thatthe heating after the formation of openings was carried out successivelyat 130° C. for 3 minutes, at 170° C. for 3 minutes, at 220° C. for 3minutes and at 350° C. for 2 minutes. The Young's modulus and glasstransition temperature of the polyimide film thus formed were the sameas those in Example 11.

[0136] At this stage, the rate of residual polarization of theferroelectric film was measured to find that it was in a value decreasedby about 5% at most, compared with the rate of residual polarization ofthe initial ferroelectric film before the coating of the polyimideprecursor solution.

[0137] Next, a finished product of a resin-encapsulated semiconductorapparatus was produced in the same manner as in Example 1, andthereafter was tested to evaluate the solder reflow resistance in thesame manner as in Example 1. As a result, like Example 1, the producthad a high reliability.

What is claimed is:
 1. A resin-encapsulated semiconductor apparatuscomprising a semiconductor device having a ferroelectric film and asurface-protective film, and a encapsulant member comprising a resin;said surface-protective film being formed of a polyimide.
 2. Theresin-encapsulated semiconductor apparatus according to claim 1, whereinsaid polyimide has a glass transition temperature of from 240° C. to400° C. and a Young's modulus of from 2,600 MPa to 6 GPa.
 3. Theresin-encapsulated semiconductor apparatus according to claim 1, whereinsaid ferroelectric film is a capacity insulation film of a capacitor. 4.The resin-encapsulated semiconductor apparatus according to claim 1,wherein said polyimide is obtained by heating a polyimide precursorcomposition at a temperature of 230° C. or above and 300° C. or below.5. The resin-encapsulated semiconductor apparatus according to claim 1,wherein said polyimide; is obtained by heating a polyimide precursorcomposition at a temperature of higher than 300° C. and 350° C. or belowfor a time shorter than 4 minutes; and has a Young's modulus of 3,500MPa or above and a glass transition temperature of 260° C. or above. 6.A process for fabricating a resin-encapsulated semiconductor apparatus,comprising the steps of; forming a film of a polyimide precursorcomposition on the surface of a semiconductor device having aferroelectric film; heat-curing the polyimide precursor composition filmto form a surface-protective film formed of a polyimide; andencapsulating, with an encapsulant resin, the semiconductor device onwhich the surface-protective film has been formed.
 7. The process forfabricating a resin-encapsulated semiconductor apparatus according toclaim 6, wherein the polyimide has a glass transition temperature offrom 240° C. to 40° C. and a Young's modulus of from 2,600 MPa to 6 GPa.8. The process for fabricating a resin-encapsulated semiconductorapparatus according to claim 6, wherein the step of heat-curingcomprises a step of curing said polyimide precursor composition film byheating at a temperature of 230° C. or above and 300° C. or below. 9.The process for fabricating a resin-encapsulated semiconductor apparatusaccording to claim 6, wherein; the step of heat-curing comprises a stepof heating at a temperature of 300° C. or above and 350° C. or below;and said polyimide has a Young's modulus of 3,500 MPa or above and aglass transition temperature of 260° C. or above.
 10. The process forfabricating a resin-encapsulated semiconductor apparatus according toclaim 6, wherein said polyimide precursor composition contains as apolyimide precursor a polyamic acid comprised of a repeating unitrepresented by the following general formula (I):

wherein R¹ is at least one of tetravalent aromatic organic groups shownin the following chemical formula group (II), and R² is at least one ofdivalent aromatic organic groups shown in the following chemical formulagroups (III) and (IV):


11. The process for fabricating a resin-encapsulated semiconductorapparatus according to claim 6, wherein said polyimide precursorcomposition contains as a polyimide precursor a polyamide acid comprisedof a first repeating unit represented by the following general formula(I) and a second repeating unit represented by the following generalformula (V): the proportion of the number of said second repeating unitto the total number of said first repeating unit and second repeatingunit being 10% or less;

wherein R¹ is at least one of tetravalent aromatic organic groups shownin the following chemical formula group (II):

R² is at least one of divalent aromatic organic groups shown in thefollowing chemical formula groups (III) and (IV):

R³ is at least one of divalent silica-containing organic group shown inthe following chemical formula group (VI):


12. The process for fabricating a resin-encapsulated semiconductorapparatus according to claim 6, wherein the heating in the step ofheat-curing is carried out using a hot plate.
 13. A process forfabricating a resin-encapsulated laminated device, comprising the stepsof; forming a film of a polyimide precursor composition on the surfaceof a laminate having a ferroelectric film; heat-curing the polyimideprecursor composition film to form a film of a polyimide having a glasstransition temperature of from 240° C. to 400° C. and a Young's modulusof from 2,600 MPa to 6 GPa; and encapsulating, with an encapsulantresin, the laminate on which the polyimide film has been formed.